The present disclosure herein relates to a flat-top mode generating device and an arrayed waveguide grating having the same, and more particularly, to a flat-top mode generating device having a double-tapered structure and an arrayed waveguide grating having the same.
Currently, in optical communication fields and photonic integrated circuit (PIC) fields, optical devices for muxing-demuxing signals may include arrayed waveguide gratings (AWGs), echelle gratings, ring filters, and mach-zehnder interferometer. Among these devices, the AWGs are the most widely used wavelength division multiplexer (WDM) devices. In the AWG field, studies on silica-based AWGs and AWGs based on silicon (Si) or indium phosphide (InP), which is a material having a greater refractive index than that of the silica, are being conducted.
When a material having a relatively great refractive index is used, the radius of curvature at which optical loss is minimized is reduced. Thus, the AWG device may decrease in size. A general AWG has an input loss of about 3 dB. Since a silicon AWG has a relatively high thermal expansion coefficient, an output spectrum of the AWG is sensitive to a temperature. Thus, when the silicon AWG is applied, it is necessary to design the AWG so that the silicon AWG operates regardless of the temperature. For this, it is common to design the AWG so that the output spectrum of the AWG is flatted to maintain a uniform output even though the spectrum changes in wavelength due to the change of the temperature.